The present invention relates to a sprayable foamed composition, and to a method of spraying the composition for covering a material to be protected such as soil, refuse at a disposal site, or other material in a stockpile to form a protective water-resistant layer thereover.
It is common in landfill or dump operations which receive garbage, trash and/or other deposits during the day to provide a covering layer of compacted earth approximately six inches to two feet deep at the end of the day. This earth layer prevents the escape of odors, the blowing of papers and other trash into the adjacent area, the proliferation of pests such as flies, rodents, and birds, and the leaching of toxic or disagreeable components from the dumped material. This cover material provision, often termed "daily cover", is frequently required by municipal, state, and/or federal regulations which govern such landfill or dump operations.
The task of placing and compacting an earth "daily cover" represents a very significant portion of the landfill operating cost since it employs significant labor and heavy equipment. Such compacted earth cover performs its principle function only for a day or so, that is, each day's garbage or trash layer is covered at the end of the day and further garbage and trash layers are then piled directly on top of the previous day's "daily cover".
Besides the cost of applying the compacted earth cover, it is recognized that multiple earth fill layers used in this way consume a significant volume of the valuable landfill space which might otherwise be used for disposal. Many areas are rapidly exhausting their available landfill acreage and reducing the consumption rate of the available landfill volume is, accordingly, desirable.
One solution to the provision of such compacted earth cover has been proposed and described in U.S. Pat. Nos. 4,421,788 and 4,519,338 in which means are disclosed for coating the landfill surface with a non-biodegradable plastic foam spray which, in effect, provides the "daily cover". An alternate solution to this problem is disclosed in U.S. Pat. Nos. 4,909,667 and 4,927,317 wherein a canvas or plastic sheet is daily retracted and extended to protect the working face of the disposal site.
Sprayable compositions have also been proposed for agricultural and erosion control purposes. U.S. Pat. No. 2,802,303 discloses a soil surface treatment utilizing a mixture of a water-soluble cellulose derivative and a finely divided expanding lattice clay for control of natural wind and water erosion of surface soil. The mixture can be applied dry to the soil surface being treated or injected into a stream of water to form a slurry which is sprayed onto the surface.
U.S. Pat. No. 3,763,072 discloses a method of forming a relatively thick semi-impervious crust on soil to inhibit erosion, or in hydroseeding applications to apply seed, fertilizer, herbicide and fibrous mulch. The method includes the step of spraying an aqueous composition onto the soil surface and allowing the composition to cure in the treated soil surface. The aqueous composition contains an aqueous 100% latex emulsion (for binding soil particles together) and sodium silicate (to assist the composition in penetrating into the soil to prevent the formation of a mere surface layer).
U.S. Pat. No. 2,961,799 discloses a sprayable latex composition for treating soil which forms a surface film intimately bonded to the soil particles. The composition includes a water-insoluble counter-penetrant (which inhibits soil penetration by the rubber, and is absorbed preferably by the soil).
Another method for inhibiting erosion and applying seed to a soil surface is disclosed in U.S. Pat. No. 3,600,852, wherein an aqueous slurry consisting mainly of gypsum (as a binder material) and a minor amount of seed is sprayed over a soil surface. The slurry can also contain minor amounts of fertilizer, high bulking water-absorbing filler materials such as cellulosic fibers to facilitate germination, and a set retarder to lengthen the setting time. Foaming agents may also be used.
Other sprayable or extrudable agricultural mulches are disclosed in U.S. Pat. Nos. 3,812,615 and 4,297,810.
Other soil sealing methods which require the composition to be mixed with the top layer of soil to provide a water holding area are disclosed in U.S. Pat. Nos. 3,772,893 and 3,986,365.